Intensity is directly quantifiable acoustically while loudness requires human listeners

Evidence

On the other hand, intensity is an acoustic variable, and we can quantify it directly using a sound level meter. We do not need a human listener in order to make measurements of sound level. The difference in how we measure loudness versus sound level has implications for how we interpret loudness data as well as highlighting why the terms loudness and intensity are not interchangeable. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 677

Categorization

• DEFINE: Clarifies why loudness and intensity are not interchangeable terms and how measurement differences shape data interpretation.